A synchronizing circuit and a timing adjusting circuit set a position of an exposure area by beam scanning as an additional value of a first setting value set in dot unit corresponding to the scanning of a pixel clock period and a second setting value set in tap unit corresponding to the scanning of a period smaller than the pixel clock period. A CPU controls the synchronizing circuit and the timing adjusting circuit so that the exposed position becomes an objective position. The CPU changes the second setting value to a first predetermined value by increasing the first setting value by one dot, in the case that the additional value is increased to reach a first threshold. Further, the CPU changes the second setting value to a second predetermined value by decreasing the first setting value by one dot, in the case that the additional value of the synchronizing circuit and the timing adjusting circuit in which the first setting value is increased by one dot is decreased to reach a second threshold smaller than the first threshold.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A light beam scanning apparatus comprising: a beam generating portion which generates a light beam; a scanning portion which reflects the light beam generated from said beam generating portion toward a scanned surface and exposes the scanned surface by scanning the scanned surface in a main scanning direction with the light beam; an exposure position setting portion for setting a position of an exposure area exposed by beam scanning of the scanning portion as an additional value of a first setting value which is set in a first unit corresponding to the scanning of a pixel clock period and a second setting value which is set in a second unit corresponding to the scanning of the period smaller than the pixel clock period; a first control portion which controls the beam generating portion and the scanning portion so as to expose the area set by the exposure position setting portion; a detecting portion which detects a position in the main scanning direction of the area exposed by the first control portion; and a second control portion including a first changing portion which increases the first setting value by one unit and changes the second setting value to a first predetermined value in the case that the additional value of the exposure position setting portion is increased to reach a first threshold so that the exposure position detected by the detecting portion becomes an objective position, and a second changing portion which decrease the first setting value by one unit and changes the second setting value to a second predetermined value in the case that the additional value of the exposure position setting portion in which the first setting value has been increased by one unit is decreased to reach a second threshold smaller than the first threshold, wherein the second threshold is separated from the first threshold by a distance corresponding to a value in which the first predetermined value is added to the value of the second unit corresponding to the scanning of the pixel clock period.
2. A light beam scanning apparatus according to claim 1 , wherein the beam generating portion generates a plurality of light beams and the scanning portion scans the scanned surface with the plurality of light beams, the apparatus further comprising: a light-emitting power control portion which controls each light-emitting power of said plurality of light beams generated from the beam generating portion; a passing position sensor which detects each passing position in a sub-scanning direction of said plurality of light beams scanned by the scanning portion; and a passing position control portion which controls each passing position in a sub-scanning direction of said plurality of light beams to a predetermined position on the basis of detecting result of the passing position sensor, wherein the controls of the passing position control portion, the first control portion, and the second control portion are performed after each light-emitting power is controlled by the light-emitting power control portion.
3. A light beam scanning apparatus comprising: a beam generating portion which generates a light beam; a scanning portion which reflects the light beam generated from the beam generating portion toward a scanned surface and exposes the scanned surface by scanning the scanned surface in a main scanning direction with the light beam; an exposure position setting portion for setting a position of an exposure area by beam scanning of the scanning portion as an additional value of a first setting value which is set in a first unit corresponding to the scanning of a pixel clock period and a second setting value which is set in a second unit corresponding to the scanning of the period smaller than the pixel clock period; a first control portion which controls the beam generating portion and the scanning portion so as to expose the area set by the exposure position setting portion; a detecting portion which detects a position in the main scanning direction of the area exposed by the first control portion; and a second control portion including a changing portion which changes the second setting value to a value in which a multiple value of the second unit corresponding to the scanning of the pixel clock period is multiplied by a multiple of a predetermined number of the first unit in the case that the second setting value is increased to a value more than the value corresponding to the multiple of the predetermined number of the first unit so that the exposure position detected by the detecting portion becomes an objective position.
4. A light beam scanning apparatus according to claim 3 , wherein the beam generating portion generates a plurality of light beams and the scanning portion scans the scanned surface with the plurality of light beams, the apparatus further comprising: a light-emitting power control portion which controls each light-emitting power of said plurality of light beams generated from the beam generating portion; a passing position sensor which detects each passing position in a sub-scanning direction of said plurality of light beams scanned by the scanning portion; and a passing position control portion which controls each passing position in a sub-scanning direction of said plurality of light beams to a predetermined position on the basis of detecting result of the passing position sensor, wherein the controls of the passing position control portion, the first control portion, and the second control portion are performed after each light-emitting power is controlled by the light-emitting power control portion.
5. A light beam scanning apparatus comprising: a beam generating portion which generates a light beam; a scanning portion which reflects the light beam generated from the beam generating portion toward a scanned surface and exposes the scanned surface by scanning the scanned surface in a main scanning direction with the light beam; an exposure position setting portion for setting a position of an exposure area by beam scanning of the scanning portion as an additional value of a first setting value which is set in a first unit corresponding to the scanning of a pixel clock period and a second setting value which is set in a second unit corresponding to the scanning of the period smaller than the pixel clock period; a first control portion which controls the beam generating portion and the scanning portion so as to expose the area set by the exposure position setting portion; a detecting portion which detects a position in the main scanning direction of the area exposed by the first control portion; and a second control portion including a changing portion which sets the second setting value to a value of a predetermined ratio to the maximum value of the second setting value so that the exposure position detected by the detecting portion becomes an objective position, decides the first setting value in which the position in the main scanning direction of the area exposed by the first control portion substantially corresponds to the objective position, fixes the first setting value to the decided value, and changes the second setting value according to the shift of the exposure position from the objective position.
6. A light beam scanning apparatus according to claim 5 , wherein the beam generating portion generates a plurality of light beams and the scanning portion scans the scanned surface with the plurality of light beams, the apparatus further comprising: a light-emitting power control portion which controls each light-emitting power of said plurality of light beams generated from the beam generating portion; a passing position sensor which detects each passing position in a sub-scanning direction of said plurality of light beams scanned by the scanning portion; and a passing position control portion which controls each passing position in a sub-scanning direction of said plurality of light beams to a predetermined position on the basis of detecting result of the passing position sensor, wherein the controls of the passing position control portion, the first control portion, and the second control portion are performed after each light-emitting power is controlled by the light-emitting power control portion.
7. An image forming apparatus comprising: a beam generating portion which generates a light beam; a scanning portion which reflects the light beam generated from the beam generating portion toward a scanned surface and exposes the scanned surface by scanning the scanned surface in a main scanning direction with the light beam; an exposure position setting portion for setting a position of an exposure area by beam scanning of the scanning portion as an additional value of a first setting value which is set in a first unit corresponding to the scanning of a pixel clock period and a second setting value which is set in a second unit corresponding to the scanning of the period smaller than the pixel clock period; a first control portion which controls the beam generating portion and the scanning portion so as to expose the area set by the exposure position setting portion; a detecting portion which detects a position in the main scanning direction of the area exposed by the first control portion; and a second control portion which controls the exposure position setting portion so that the exposure position detected by the detecting portion becomes an objective position, the second control portion being provided with one of a first changing portion, a second changing portion, and a third changing portion which are shown in (a) to (c): (a) a first changing portion which increases the first setting value by one unit and changes the second setting value to a first predetermined value in the case that the additional value of the exposure position setting portion is increased to reach a first threshold, and decrease the first setting value by one unit and changes the second setting value to a second predetermined value in the case that the additional value of the exposure position setting portion in which the first setting value has been increased by one unit is decreased to reach a second threshold smaller than the first threshold, wherein the second threshold is separated from the first threshold by a distance corresponding to a value in which the first predetermined value is added to the value of the second unit corresponding to the scanning of the pixel clock period; (b) a second changing portion which changes the second setting value to a value in which a multiple value of the second unit corresponding to the scanning of the pixel clock period is multiplied by a multiple of a predetermined number of the first unit in the case that the second setting value is increased to a value more than the value corresponding to the multiple of the predetermined number of the first unit; and (c) a third changing portion which sets the second setting value to a value of a predetermined ratio to the maximum value of the second setting value, decides the first setting value in which the position in the main scanning direction of the area exposed by the first control portion substantially corresponds to the objective position, fixes the first setting value to the decided value, and changes the second setting value according to the shift of the exposure position from the objective position, and an image forming portion which determines an image forming area on an image carrier on the basis of the first setting value and the second setting value of the exposure position setting portion and forms an image corresponding to input image data on the image forming aria using the beam generating portion.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
May 28, 2003
September 14, 2004
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